1. Field of the Invention
The present invention relates to a gas-liquid separator that can receive a sample gas into a gas-liquid separating chamber to enable a separation of gas from any liquids and/or solids by a centrifugal process and more particularly to an improved gas-liquid separator that can accommodate various pressure fluctuations in the sample gas.
2. Description of Related Art
Various types of gas-liquid separators have been utilized, for example, in analyzing the constituents existing in the exhaust gas of a motor vehicle to quantify the amount of air pollution. In this field, various kinds of gas-liquid separators for initially separating a sample gas having impurities from a liquid by a centrifugal processing have been utilized prior to providing the sample gas to an infrared analyzer for determining various air pollutants in the exhaust gas, such as CO.sub.2, NO.sub.x, HC and the like. An infrared analyzer that is used to analyze the air pollutants requires the gas sample to be appropriately prepared prior to an application of infrared rays in the measurement cycle. If, for example, moisture and solid impurities are introduced into the testing chamber of the infrared analyzer significant errors can occur. Thus, a gas-liquid separator having a high efficiency is particularly desired to prepare the gas specimen.
Referring to FIG. 3, a gas-liquid separator utilized in the prior art is disclosed. This gas-liquid separator 20 can be positioned between an engine exhaust pipe (not shown) and an infrared analyzer (not shown). A body portion 2 of the separator is provided with a gas-liquid separator chamber 3', a centrifugal separator assembly 4 and a drain pot 5. The gas-liquid separating chamber 3' is essentially a hollow chamber that communicates with a sample gas introducing pipe 6 that can be connected to the exhaust pipe of an engine at one end thereof. A second sample gas discharging pipe 7 can be connected to a vacuum section pump (not shown) for drawing off sample gas. The centrifugal separator 4 includes a motor 4a and an upper rotating plate 4b positioned in the hollow chamber. The motor 4a is arranged below the gas-liquid separating chamber 3' and an axis of a shaft of the motor 4a coincides with a longitudinal axis of the sample gas discharging pipe 7. A relatively small gap (g) or distance is provided between the upper surface of the rotating plate 4b adjacent the respective openings of the gas introducing pipe 6 and the sample gas discharging pipe 7 and the upper interior surface of the gas-liquid separating chamber 3' so that any sample exhaust flowing into the gas-liquid separating chamber 3' through the sample gas introducing pipe 6 will have any impurities of liquid and solid material discharged radially outward from the rotating plate 4b to ensure that any gas sample withdrawn by sample gas discharging pipe 7 will be free of such impurities.
A drain pot 5 is detachably mounted to the separator housing 2 and is capable of storing both liquid and solid impurities. This liquid storing vessel 5 is preferably made of glass or a transparent plastic and is screwed into a threaded connection formed adjacent an exhaust passage or port 3a' of the gas-liquid separating chamber 3'. Additionally, an end portion of a bypass pipe 8 is capable of communicating with a vacuum suction pump for use as a bypass (not shown) and can extend above the drain pot 5 so that the gas-liquid separating chamber 3' can be kept at a negative pressure to facilitate the introduction of any separated liquid into the drain pot 5. While not shown, the sample gas discharging pipe 7 can be provided with a pressure regulator so that a gas pressure of the gas sample supplied to an infrared analyzer can be regulated to a specific gas pressure level and the amount of sample gas introduced into the sample gas discharging pipe 7 is effectively controlled.
In operation, when an exhaust gas sample is introduced into the gas-liquid separator 20, both the vacuum suction pump for withdrawing a portion of the sampled gas and a vacuum suction pump for use in the bypass passageway 8 are started to maintain the gas-liquid separating chamber 3' at a negative pressure of approximately -0.3 Kgf/cm.sup.2. During this time period, the centrifugal separator assembly 4 is operated so that when the exhaust gas discharged from the engine is introduced into the gas liquid separating chamber 3' by the conduit or pipe 6, it will contact the rotating plate 4b. Any liquids, such as water drops, and small particular solids, such as soot, that come into contact with the rotating plate 4b will be accelerated at a relatively high speed to be blown radially off of the rotating plate 4b in a centrifugal separation process. Such action will separate the exhaust gas with the sample gas being withdraw through the discharging pipe 7. The liquids and particulate materials that are separated are drawn by the negative pressure into the drain pot 5 for storage and subsequent discharge. As can be appreciated, the quantity of the liquids and solid particulates stored in the drain pot 5 will be progressively increased throughout the operation of an exhaust gas sampling procedure. An operator is required to monitor the drain pot 5 and to suitably remove it during a continuous analysis of the exhaust gas. This can cause maintenance problems and requires constant monitoring to ensure the proper operation of the gas-liquid separator 20.
In addition, the gas-liquid separating chamber 3' is designed to be kept at a negative pressure and there is always the possibility of a loss of such negative pressure by virtue of the bypass pipe 8. The suction pressure of a vacuum suction pump (not shown) connected to the bypass line 8 is not adapted to follow any internal pressure changes in the gas-liquid separating chamber 3' that can result with a fluctuation of the output of an engine. As a result, when the output of the engine is increased the internal pressure of the gas-liquid separating chamber 3' will also increase and the negative pressure condition that is desired can be lost and frequently it becomes difficult to draw or suck the centrifugally separated liquid and solid fraction toward the side of the drain pot 5. Also, the separated liquid and solid fraction can also be drawn directly into the bypass pipe 8 under certain circumstances and can clog up the bypass pipe 8 in an extreme case thereby disrupting the operation of the gas-liquid separator.
The prior art is still attempting to optimize the performance of gas-liquid separators.